Induction electric furnace



Nov. 3,-1931. E, F. NoRTHRUP 1,830,481

INDUCTION ELECTRIC FURNACE Filed July 16. 1929 4.0 tion by one PatentedNov. 3, 1931 UNITED s'rAT'Es PATENT; orFlCa EDWIN FITCH NORTHBUP, OFPRINCETON, NEW JERSEY, ASSIGNOB TO AJAX ELEC- T ROTHEBIIC CORPORATION,Ol' PARK, NEW JERSEY, A CORPORATION OF NFW JERSEY Application med July1s, i929. serial m. 378,622.

My invention relates to furnaces which are intended to'hold a content orcharge of material which is leasilycontaminated by the Crucible used. 5A purpose ofthe invention is tomake a furnace \crucible of sectionalconstruction comprising all light sections which are easily formed andeasily handled.

A further purpose is to form a Crucible of Y 1Q. horizontally dividedsections, electrically Conducting or non-Conducting according to I' theneeds of the furnace.

' lA further purpose is to Aapply sectional furnace construction toelectric induction .15 furnaces, making each section a separate in?ductor secondary and placing the secondaries electrically in parallel.

A further purpose is to provide a furnace made uplof sections which maybe held to'- gether by their weight and whichmay be sealed further andadditionally secured in position b 'aj surrounding tamped finelydividedre actory. A further purpose is to provide a furnace p, "'5 madeup ,of a series of rings divided in horizontal planes permittingvariation" in the shape of the furnace by change inthe rings selected. Y

A further purpose is to provide a furnace particularly suited to themelting of glass of special quality.

A further purpdse is to provide a furnacewhich is readilymanufactured-from materials which are-difficult toV cast in large unitsbut which may be very desirably free from contaminating ingredients.

` Further tpurposes will appear inthe specifiction an i the claims.

I have preferred to illustrate my invenneral form only, selecting a formwhich 1s practical, ellicientxand relatively in 've and which is wellsuited to the'service for which it is intended.-

Figures 1 and 3 are'central vertical sections lof slightlydiierent'forms of my invention. i I

" Figure 2 is a section taken upon line 2--2 .of 1ligure 1 i e 4 is aerspective view of one of i therlsofmyfrn ce INIDU'CTION ELECTRICFURNACE In furnace practice considerable diiliculty is found inhandling" some of the charges because they are quite sensitive tocontamination by the materiall of the Crucible or otherccontainer inwhich they are held. In some arts this seriously interferes with properheating, melting and holding of the charge.

'One example of this is found in the glass art where high grade glassintended for optical uses or for Pyrex glass has been found to be very'easily contaminated by the usual crucible materials.

vGlass is electrically non-conducting and the heat must bedeveloped inthe container. Glass melts at a low enough temperature to l be meltedwithin a metal pot or Crucible, but

the'met'als whic are best suited otherwise for Crucible purposes are notfree from contaminating effect upon the glass. On the other hand some ofthe best metals from the -rious alloys of tungsten carbide and nickelwhich are non-contaminating with respect to glass and excellent for thepurpose 1n varying percentages of carblde and mckel and operate Wellwith 80% tungsten carbide and 20% nickel. This alloyis difficult to eastin large units.'k

My invention is designed to make metals and such alloys fully availablefor furnace purposes byproviding for sectional furnace construction. Itoffers a sectional' construcltion which is simple`and inexpensive andwhich hasmany advantages in addition to its adaptability for use withspecial metals.

Describing in illustration and not in limitationzf The furnaceillustrated is made up'V of rings which can be separately cast andiinished and can be built up into Crucible form by mounting one ringupon another ntil the desired furnace height is reached.

Crucible 5 is made u -of 'a base 6 and a plurality of rings? which maybeof equal diameter to make a cylindrical crucible, as in Fi re 1, .or ofdifferent diameter as at 7 in igure 3 or shape to give any desiredcontour to the furnace.

The invention is particularly well suited to the coreless t e ofelectric induction furnace, such as in igures 1 and 3. v

In these figures I have shown a coreless type furnace inductor 8surrounding the composite crucible and supplied with electric current asconventially illustrated byl leads 9 and 10 across which-is placedpowerfactor-corrective capacity 11. The turns of `the inductor maybewater-cooled if desired whenever the temperature Ato be attained.]us

tiies it.

The coil is shown as insulated interiorly at 12 by any-suitable'shell13, such asl micanite, and is spaced' from the crucible at 14 by anysuitable material or materials which will shown-may e ge.

Ben th the crucible the refractory rests upon an suitable bottom16'which is extended to carry the coil at 17 The`furnace is encasedwithin an outer frame 18 supported b trunnions 19 from links 20 f y Theouter frame or shell 21 may be of non# magnetic material .as in Figure3, ormay be magnetic and be protected from stray field by any suitablemeanssuch as ma turn. circuit 22.v Such a magnetic return circuit shouldbe laminated and may convenientl extend across beneath the bottom of theace as well as up the sides at any desired number of locations about thefurnace circumference.

I have shown a conventional ofthe upper part of the furnace. in thespacing of the outer'fra'nie or shell 21 from the refrac- .horizontalparallel .ary paths in Vparallel withinwliich current tory 15 byfa ring23 .of some such material as asbestos lumber. v Y

Y In Figure 3=thei`bottom is supported from the lower artv of the shellby a spacer`24.

-It will llie evident that the subdivision of the crucible into sectionsis desirable whatever the sections and that subdivision alo planesprovides secon 'will be induced b v-the normal vertical fur- A iliaceinductor-J The resultant structure 'is therefore 'of maximum advantagefrom standpoints both of construction and operation. It further reducesrepair and replace-V vided refractory fractory meut costs since in caseof inury the par@ ticular section injured alone will need be replaced. ff

For most of the services requiredthe env Vides heat insulation,additionally insuresv against displacement ofrthe sections from theirsealing contact and closes the s ace about the sections against passageof lea a e charge which may tend to pass through t e joints between thesections.

The holding power of the-.tamped refractory and of the refractorysection at the top ofthe furnace are uite desirable to hold the sectionsagainst re ative movement during pouring. v

In view of my invention and disclosurevariationsl and modifications tomeet individual whim'. o'r articular need will doubtless become evi entto others skilled in the art to obtain all or part of the benefitsofvmyinvention without copying the structure shown, and I, therefore,claim all such in so far as they fall within the reasonable spirit and,

sco` of m invention.

aving us described my invention, what ters Patent is:-

section and metal rings restin upon the bottom and successively u on eacother to make up the side walls of .t e crucible.

' 2. A furnace crucible having side walls of electrically conductingmetallic rings adapted to rest one upon another.

3. A furnace crucible having side walls of electrically conductingmetallic adaptedtorestoneu nanotherand contaminating e ect upon theintended melt.

4.- An induction electric furnace crucible comprising a bottom section,a lurality of detachable short electrically con ucting me tallc one onanother and a coreless inductor surrounding the crucible' and adpted toinduce secondaryllow of current iii e sections in 5. In an electricinduction furnace, a crucible made up of horizontally dispod metallicrings resting one upon another, an inductor coil surroun the crucibleand finely dirammed between the. coil and crucible and adapted to holdthe rin in position by firm engagement with their `exterior surfaces.

^ 6. A crucible comprising a bottom section and a lurality of ringstogether forming side wrs, a refractory material outside the rings, an'inductor coil surrounding the reand a magnetic circuit for return fluxoutside of the inductor.

froml 7. A crucible adapted to form Valt` of a furnace bodlylfngndcomprising an Sloy lof tungsten carbide and-nickel.

8. A crucible ring adapted to form part of a furnace body and comprisingan electrically conductive metal dicult to cast in large units.

9. A glass melting furnace comprising a bottom section and rm of analloy of tungsten carbide and nicke a. refractory packed about thecrucible .and a furnace inductor surrounding the refractory andcrucible.

v10. A glass melting furnace comprislng a bottom section and rings of anelectrica ly conducting metal non-contaminatin to glass, a .refractorypacked about the cruci le and a.

furnace inductor surrounding the refractory and crucible.

EDWIN F. NORTHRUP.

